Power generation

Importance of Electricity
Electricity is a very convenient form of
power for
 Lighting,
 Motive power for driving various load
and
 Power for a No. of utilization applications.
Generally it is economical and easier to use
this form of power.
Its other advantages are ease of control and
cleanliness.

Importance of Electricity
The annual consumption of electrical
energy has been increasing rapidly
throughout the world.
The standard of living, in a country, has
relation, to a certain extent, to the
consumption of electricity in that country.
Rapid industrialization becomes possible
when cheap electric power is available.
With industrialization, the standard of
living improves.

Components of Power System
The main components of an Electric
Power System are:
1. Power Station
2. Transmission System
and
3. Distribution Network.

POWER STATION
An electric power station is a factory in
which energy is converted from one form
or another into electrical energy.
These power stations can be categorized
into the following types:-
i). Thermal Power Stations.
ii). Hydroelectric Power Stations.
iii). Solar (Photo Voltaic) Power Plant
iv) Wind Power Plant

Thermal Power Stations
In thermal power stations, the Heat Energy
of fuel or source is first converted into
mechanical energy by the help of a turbine
or engine, which in turn drive a generator
to produce electrical energy.
The Thermal Power Stations can be
subdivided into the following types of
power stations.
a. Conventional or fossil fuelled
b. Nuclear
c. Solar
d. Geothermal

CONVENTIONAL/FOSSIL-
FUELLED POWER STAIONS
These power stations can be sub divided
into following types:-
i. Diesel electric power stations
ii. Steam power stations
iii. Gas turbine power stations
iv. Combined cycle power plants

Diesel Electric Power Plants
In this type of power stations, chemical
energy in a fuel, normally high speed
diesel oil, is converted into mechanical
energy by the help of a diesel engine. The
diesel engine is further used to drive an
electric generator which produces
electrical energy.
The size of such a plant varies from very
small units to bigger units, such as upto
25MW.

The advantages of a Diesel electric
station are as under:-
i. It can be started and stopped quickly as and
when required.
ii. It does not need any warming period and
need not be kept running for a long time
before picking up load.
iii. It does not need a large amount of water
for cooling
iv. It does not need a larger space
v. It takes less installation time as compared to
turbines.

The main applications of diesel electric stations are as under:-
i. Standby-plant
A diesel electric station may be used as a standby plant to supply part of the load in
a power system when required. It can be used in conjunction with a hydro station if
the reservoir level falls down due to reduced rain-fall and in conjunction with a
steam power station to supply a part of load, on the failure of a steam unit.
ii. Emergency Plant
It can be used as a start up unit for a steam unit if the grid system fails and there is
no supply available to start the steam unit.
iii. Peak-load Plant
It can be used to supply peak load on the Power system while the base load is
supplied by the steam or hydro stations. The base load factor will thus be improved
and the cost of electrical energy per kilowatt hour will be reduced.
iv. Private power plant for small industries
These plants have applications as private industrial plants supplying electric power
to factories because they have many advantages over steam units such as
requirement of less space and cooling water, less manpower, ease of operation and
maintenance etc.
v. Nursery Stations
The diesel electric plants can be installed in remote and sparsely populated areas
which have less load and it is not economical to connect these areas to an existing
grid system. When the load in this area increases and it becomes more economical
to connect to the grid, then nursery plant is shifted to another place.

Steam Power Stations
In a steam power station, the chemical
energy in a fuel is changed to heat energy
by combustion in a boiler furnace which is
used to convert water into steam at high
pressure and high temperature. The high
pressure high temperature steam is used to
drive a steam turbine and thus heat energy
stored in steam is changed into mechanical
energy. The steam turbine then drives a
generator which produces electrical energy.

i. Private Industrial Plants
Industries requiring steam for process purposes
may be able to use their steam plant for electrical
power production as well. However, before
deciding to build a private power station, it is
necessary to consider its economics as compared
with taking a supply from some external source
such as grid.
ii. Central Stations
The steam power stations can be used as central
base stations to supply power to the grid in bulk.
The sizes can vary from small stations to large
stations such as 1000MW power plant unit.

Considering the type of fuel used, the
steam power plants can be of the
following types.
a. Coal fired power plants.
b. Oil-fired power plants.
c. Gas-fired power plants.
d. Dual fuel fired power plants.

Main Components
The main parts of a steam power station are:
Boiler or Steam generator
Steam Turbine
and Electric Generator
• In the boiler fuel is burnt to change its chemical energy into heat energy. The heat
energy so produced is used to convert water into steam at the required pressure and
temperature. Generally water tube boilers are used for electric power stations. The
boiler consists of a number of drums and a set of tubes connected to these drums, in
which water provided by a feedwater system, is converted into steam. The heat transfer
takes place through the walls of the tubes and the drum or drums are protected from
direct contact with the hot flue gases. The steam is superheated in a superheater before
passing from the boiler to the turbine.
• The high pressure, high temperature superheated steam is passed through a high
pressure turbine, which has a number of rows of fixed and moving blades to convert
heat energy in the steam into rotation of the turbines shaft and thus mechanical energy.
There can be only one turbine or a number of high pressure and low pressure turbines,
tandem compound. The exhaust steam which is low pressure at low temperature is
normally condensed to water to use it again as feedwater for the boiler.
• The turbine is coupled to the generator and thus mechanical energy produced in the
turbine is used to generate electrical energy.

GAS TURBINE POWER STATIONS
In gas turbine power stations, fuel is burnt in a combustion chamber and the
hot gases so produced are passed directly through a turbine to convert heat
energy of hot flue gases into mechanical energy which is available at the
turbine shaft and can be used to drive a generator to generate electrical
energy.
The main parts of a gas turbine power station are as under:-
1. The compressor
2. The combustors
3. The turbine
4. The Generator
The compressor compresses the atmospheric air to about 8-10 times and
delivers it to the combustion section at high temperature and high
pressure. In the combustion section fuel is burnt to convert this
compressed air into high temperature/high pressure flue gases.
These gases are passed through a special turbine, called gas turbine, to
convert the heat energy into mechanical energy. The turbine, in turn, is
used to run the compressor and the generator.

GAS TURBINE POWER STATIONS
The advantages of a gas turbine power stations are
as under:-
1.As a peak load plant
2.Very low cooling water requirement
3.Very short commissioning time as compared to a
conventional steam power plant
4.Very less staff requirement
5.Very short starting/stopping time
6.Low initial cost as compared to conventional
steam plants
7.Very quick starting and loading. Therefore, very
quick restoring of Grid on system failures.

COMBINED CYCLE POWER PLANTS.
The exhaust gasses from the gas turbines are at
very high temperatures such as between 500°C to
550°C. In this way, the exhaust gases carry a lot of
heat with them to the atmosphere which is a very
big loss. These flue gasses, if routed through a Heat
Recovery Steam Generator can produce steam
which can run a steam turbine coupled with a
generator to produce electrical energy. In this way
the efficiency of the plant can be increased from
about 30% to about 45%. The steam turbine can
develop almost half power as generated by the
associated gas turbines.

A simplified diagram of a Combined Cycle
Power Plant
Electric
Generators
Steam Turbine
Condensor
Feed Pump
Gas Turbine
Boiler/
HRSG

The conventional thermal power stations use oil, coal or gas
as the source of heat energy. The reserves of these fuels are
becoming depleted in many countries, and thus there is a
tendency, worldwide, to seek alternative sources of energy.
The nuclear power station has a some of advantages over
the conventional thermal power stations.
1. It reduces the demand for coal, oil or gas, the costs of
which are tending to rise.
2. The transport of conventional fuel to the power station
involves cost as well as time delay.
3. The weight of the nuclear fuel required for a station of
the same capacity is almost negligible and these
problems do not arise.
4. The nuclear power station needs less area and volume
compared to a conventional plant of equal capacity.
NUCLEAR POWER PLANTS

In a nuclear power
station, instead of a
furnace, there is a
nuclear reactor, in
which heat is
generated by
splitting atoms of
radioactive
materials such as
uranium, under
suitable conditions.

The main parts of a nuclear power station are as under:
a. Nuclear reactor
b. Steam Turbine and Condenser
c. Generator
In a boiler furnace, heat is produced by burning fuel. In a nuclear reactor,
heat is produced by the fissioning, or splitting, of uranium atoms.
A cooling medium takes up this heat and delivers it to the heat exchanger
where steam is generated to run the steam turbine.
The reactor and heat exchanger are equivalent to the furnace and boiler
in a conventional steam plant. The rest of the plant is similar to the
ordinary steam plant.
The steam generated in heat exchanger is admitted to the turbine, and
after work has been done by the expansion of steam through the
turbine, the steam is condensed into condensate in the condenser.
The other auxiliaries are similar to those in a conventional steam
power station.

Geo Thermal Power Plants
• The Earth's crust is a bountiful source of energy—and fossil fuels
are only part of the story. Heat or thermal energy is by far the more
abundant resource. To put it in perspective, the thermal energy in
the uppermost six miles of the Earth's crust amounts to 50,000
times the energy of all oil and gas resources in the world
• A geothermal power plant uses its geothermal activity to generate
power. This type of natural energy production is extremely
environmentally friendly and used in many geothermal hot spots
around the globe.
• To harness the energy, deep holes are drilled into the earth (much
like when drilling for oil) until a significant geothermal hot spot is
found. When the heat source has been discovered, a pipe is
attached deep down inside the hole which allows hot steam from
deep within the earths crust to rise up to the surface.
• The pressurized steam is then channeled into a turbine which
begins to turn under the large force of the steam. This turbine is
linked to the generator and so the generator also begins to turn,
generating electricity.
• Cold water is pumped down through a new pipe which is heated by
the earth and then sent back up the first pipe to repeat the process.

Flashed Steam Geothermal Process

SOLAR POWER STATIONS
Concentrated solar power also called
concentrating solar thermal, systems use
mirrors or lenses to concentrate a large area of
sunlight, or solar thermal energy, onto a small
area. Electrical power is produced when the
concentrated light is converted to heat, which
drives a heat engine (usually a steam turbine)
connected to an electrical power generator.

Solar Power (Heat Concentrated)
• Parabolic Trough

Dish Striling
A parabolic solar
dish concentrating
the sun's rays on
the heating
element of a
Stirling engine. The
entire unit acts as
solar tracker.

Solar Power
Tower
The PS10 Solar Power Plant
concentrates sunlight from a field
of heliostats onto a central solar
power tower.

Compact linear Fresnel
reflector
Incident solar rays are concentrated on
insulated steam tubes to heat working
thermal fluid.
CLFR solar systems alternate the inclination of
their mirrors to focus solar energy on multiple
absorbers, improving system efficiency and
reducing overall cost.

Hydro Electric Power Stations
Where water resources are available, hydro
electric power stations are built to generate
electrical energy. These power stations, however,
cannot be located anywhere.
There must be an ample quantity of water at
sufficient head and a suitable site must be
available.
The possibility of constructing a dam at a suitable
site to store water in the catchment area and the
availability of water throughout the year are the
decisive factors.

Hydro Electric Power Stations
Main Components
i. Dam The dam is a barrier to confine water for storage and to raise its level to
create a water head. A dam helps in diverting the flow of water from the river
to the turbines at increased head.
ii. Spillways All the dams used for power stations are provided with spillways to
discharge excess water in the reservoir beyond the full permissible level.
iii. Forebay The forebay is the enlarged body of water just above the intake. This
may either be a pond behind the diversion dam or an enlarged section of a
canal spread out to accommodate the required width of intake.
iv. Intake The function of the intake in a hydro electric project is to let water
into the conduit or penstock under controlled conditions.
v. Penstock From the intake works and forebay, water is taken to the turbines
by a conduit system known as penstock.
vi. Turbine The turbine converts the potential and kinetic energy of water into
mechanical energy. The turbine, further runs to generator to produce
electrical energy.
vii.Generator The turbine, further runs to generator to produce electrical
energy.

Tidal Energy
• Tidal power sometimes also called tidal
energy, is the form of hydropower that
converts the energy of tides into electricity or
other forms of energy.
Types of Tidal Energy
• Barrages (potential energy)
• Tidal Streams (kinetic energy)

SOLAR POWER STATIONS
The solar power stations, smaller in size, convert
the heat energy of the sun into electrical energy.
For this purpose arrays of special collectors
made of silicon are used to collect and convert
heat energy into electrical energy. The amount
of electrical energy produced depends upon the
area of the collectors and the time exposure the
sun. This type of power stations are at present,
in experimental stages.

Solar Power (Photo Voltaic)
Components of a typical standalone PV
system using crystalline silicon technology.

Wind Energy
• A wind turbine is a device that converts
kinetic energy from the wind, also called
wind energy, into mechanical energy; a
process known as wind power.
• If the mechanical energy is used to
produce electricity, the device may be
called a wind turbine or wind power
plant.
• If the mechanical energy is used to drive
machinery, such as for grinding grain or
pumping water, the device is called a
windmill or wind pump.
• Similarly, it may be referred to as a wind
charger when used for charging
batteries.

Power generation

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